从 redux-saga 调用组合重选选择器

Question

我正在尝试从redux-saga 调用组合选择器。这个想法是我有两个下拉菜单。第一个下拉菜单中的选择将过滤第二个下拉菜单中的适当值，即我的组合选择器将过滤掉一些不相关的值，因此它们不会显示在第二个下拉菜单中：

1) 我有两个选择器，firstSelector 和 secondSelector

// firstSelector returns {"Cat":["black","white"],"Dog":["grey"]}
const firstSelector= () =>
  createSelector(selectPage, substate => substate.firstDropDown);

// secondSelector returns ["black","grey"]
const secondSelector= () =>
  createSelector(selectPage, substate => substate.secondDropDown);

2）我将它们组合在组合选择器中（应该返回["black", "grey"]，即过滤掉“白色”）

const filterBySelection = (firstSelector, secondSelector) =>
  createSelector(
    [
      firstSelector, 
      secondSelector, 
    ],
    (first, second) => {
      const filteredValues = Object.keys(first).reduce(
        (r, k) => r.concat(first[k]),
        [],
      );
      return second.filter(val => filteredValues.indexOf(val) >= 0);
    },
  );

3) 但是如何在redux-saga 中调用filterBySelection？ 我试过了：

const filteredValues = yield select(
  filterBySelection,
  firstSelector,
  secondSelector,
);

和

const filteredValues = yield select(
  filterBySelection(firstSelector, secondSelector)()
);

和

const filteredValues = yield select(
  filterBySelection(firstSelector, secondSelector)
);

但是这些方法都行不通。

不过，我可以打电话给firstSelector 或secondSelector，即有效：

const firstData= yield select(firstSelector());

有人可以说我可以在 redux-saga 中简单地做到以下几点：

const first = yield select(firstSelector());
const second = yield select(secondSelector());
const filtered = Object.keys(first).reduce(
  (r, k) => r.concat(first[k]),
  [],
);
const secondFiltered = second.filter(
  val => first.indexOf(val) >= 0,
);

但那将是not memoize，这个想法是memoize。

那么是否可以在 redux-saga 中使用 memoized 选择器？

最好的问候

Answer 1

您似乎错过了调用该函数以返回选择器。所以，要么：

一）

const filterBySelection = (firstSelector, secondSelector) =>
  createSelector(
    [
       firstSelector(), // <- parentheses 
       secondSelector(), // <- parentheses 
     ], ... )

然后：const filteredValues = yield select( filterBySelection(firstSelector, secondSelector) );

b) 正确传递选择器

const filteredValues = yield select(
  filterBySelection(firstSelector(), secondSelector())
);

c) 定义firstSelector 和secondSelector 不带函数（也许是最真实的方式）：

const firstSelector = 
  createSelector(selectPage, substate => substate.firstDropDown);

const secondSelector = 
  createSelector(selectPage, substate => substate.secondDropDown);

然后

const filteredValues = yield select(
  filterBySelection(firstSelector, secondSelector)
);

希望对你有帮助。

Answer 2

我会选择这样的东西

  createSelector(
    firstSelector, 
    secondSelector, 
    (first, second) => {
      const filteredValues = Object.keys(first).reduce(
        (r, k) => r.concat(first[k]),
        [],
      );
      return second.filter(val => filteredValues.indexOf(val) >= 0);
    },
  );```